On blogger/blogspot there is a security feature that prevents the loading of http: links in https: content (like blogger/blogspot). I don't know if it's a new feature, but it can prevent latex rendering on some browsers. If you're having trouble, replace the url to the MathJax.js library with:https://c328740.ssl.cf1.rackcdn.com/mathjax/latest/MathJax.js

It's not pretty, but it's a legit https link to the mathjax library. It is discussed on the official mathjax site here: http://www.mathjax.org/resources/faqs/#problem-https